Best Diesel Fuel Additive

First, why do I feel qualified to educate and inform on the best diesel fuel additives? Experience and education! I grew up around heavy equipment and large diesel vehicles and learned to drive on a Ford Excursion with the old 7.3 liter displacement engine. In maintaining and replacing parts on diesel engines, cars, and trucks, I have seen or experienced the problems diesel fuel additives can correct.

Much like gasoline engines, diesel engines can develop problems over time and even a little knowledge can go a long way in helping a vehicle’s owner prevent a lot of heartache down the road (or fix heartache quickly in some cases if the problem has already come up).

As many drivers already know, an ounce of prevention is worth a pound of cure. You take care of your oil, your filters, your headlights, tires, and probably even pay attention to your tailpipe for excessive wear or damage to ensure safe rides. But how do you ensure the quality of your fuel?

Do you own a diesel? Ever considered owning one? Diesel engines have several advantages. Better fuel MPG (mileage, miles per gallon) than gasoline engines, lower taxes on CO2 emissions due to cleaner exhaust fumes, lower risk of vapor lock, decreased maintenance and better lifespan, decreased fire hazard (it is harder to ignite diesel fuel), and provide much more power for their weight than gasoline engines.

Diesel power is well-known for its unquestionably higher torque. Diesel engines are built to provide a lot of power for a long time with little fuel, but over time they can fall prey to several issues: dirty injectors, low-cetane fuel, fuel cold flow issues, and frozen fuel. Diesel fuel additives can help overcome these problems, acting as preventatives for problems and reducing damage and need for maintenance over time.

In this article I will be detailing some of the best diesel fuel additives you can use and providing links. If you are just looking for the links, skip to the end of the article and look at the table! If you enjoy understanding more and enjoy my delivery, read below:

As discussed, we can have several problems with diesel engines. Many diesel fuel problems and their deleterious effects can be treated by using diesel fuel additives. We will touch on these problems and the consequences of leaving them untreated.

I hope to offer more insight than typical diesel fuel additive reviews. I am also going to discuss why we want our system to be protected by additives, not just for a cleaner fuel system, but to supplement smoother engine running and ensure that you reach maximum horsepower.

Dirty fuel injectors: When clean, diesel fuel injectors will atomize (create a very fine spray) of diesel, usually in a five-pointed star pattern. This disperses the fuel evenly and ensures even combustion in the cylinders, leading to good engine performance and ensuring adequate power during acceleration, when driving uphill, and when hauling. If they get dirty, engine power will decrease especially under load when it is most needed from the crud blocking the fuel injector.

Fuel system preventative maintenance is critical to limiting cost over the life of an engine and using diesel fuel additives is a major part of any engine treatment plan. With diesels, understanding cleaning fuel, filtration of fuel, and stabilizing fuel (for long term storage for farming, power generation, or at a refinery), are all a useful part of fuel smarts.

Dirty fuel injectors can be cleaned with a fuel additive specifically formulated with detergents to help remove the deposits. They are less necessary if very high grade fuels are used (from gas companies that add detergents and other additives to keep them clean), but if you burn regular diesel fuel, it is a good idea to use one. It cleans and protects your injectors and works along with diesel conditioner additives to round out your fuel treatment plan.

You do want to be careful about what kind to use. Some use harsh, aggressive detergents that decrease the lubricity of your fuel. Not a good idea. Despite the improvements in fuel injector cleanliness, the decreased lubricity can lead to increased wear and tear on the engine. Diesel engines rely heavily on the fuel to lubricate and cool components more than a gasoline engine and a modern diesel vehicle’s highly refined fuels have to be altered with lubricants just to increase their lubricity.

A high-quality injector cleaner can clean your injectors and increase lubricity. This is unusual and highly desirable. We will look at a product like that later in the article (or remember you can skip to the end to see the table now!

Low cetane-fuel: Octane in gasoline is a measure of how difficult it is for the fuel to ignite before it should. Higher octane fuels ignite only when the spark plug goes off, ensuring that there is no premature firing that can lead to loss of power. Cetane, on the other hand, is a measure of how easily diesel fuel ignites. Diesel engines use no spark plugs. A diesel vehicle’s fuel is ignited using extreme compression and glow coils.

That said, it is pretty easy to remember the practical result: The higher the octane value, the better the fuel – up to a point. Boosting the cetane rating higher gives us better diesel fuel – also up to a point. Different engines and manufacturers will have different recommended cetane ratings for diesel fuel. The minimum required in America is 40, with most lower grade fuels being a little higher than that. That said, California requires a minimum of 53, and many counties in Texas require 48 or more.

Bottom line: In most states, if you are not buying a premium fuel with special additives to increase the cetane rating, your fuel is providing your engine less power than it could. Fortunately, you can use cetane booster additives to increase the cetane value of your diesel fuel. Cetane boosted fuel will ignite effectively and burn more completely to keep your engine running smoothly and efficiently. This is especially important with biodiesel and blended fuels.

As with injector cleaner, you want to make sure you are using a high-quality product. A low quality, cheap additive can be harmful for your engine, particularly if it is one of the leftovers from an era when most additives were designed for older, lower-tolerance diesel engines. Cheap additives can also have corrosive contaminants. Such contamination can degrade and damage your engine. The best diesel additives are modern and developed by companies with experience in both diesel and gasoline engines.

Next, we have anti-gelling agents or cold-flow agents. One of the disadvantages of diesel fuel is fuel gelling. Diesel fuel can thicken and gel at low temperatures or even solidify at very, very low temperatures. This happens because one of the components in diesel fuel is paraffin. This is a wax we most commonly associate with candles – which are obviously solid.

Most untreated diesel fuels will gel at -18 degrees Fahrenheit, but some will start to thicken much earlier, some as warm as 40 degrees Fahrenheit. If you want to use your diesel fuel (even summer diesel fuel!), it can be done relatively inexpensively.

There are a few ways around this problem. The first method, unmatched for efficacy, is unfortunately also impractical: it is to keep the vehicle parked indoors in a heated environment at all times. Not practical if you drive to work and park in a parking lot instead of a private, heated garage – and since I am a working man writing for working men, I tend to steer aware from solutions that aren’t available to someone that may work where they can’t park their vehicle in a climate controlled environment.

Another solution is to use a fuel warmer. You can buy these and install them in your vehicle, but that requires a significant amount of know-how and add something else to break on your car. Any additional electronics component in a vehicle is another piece of delicate equipment that can easily malfunction.

Lastly, and my favorite, you can use a diesel treatment that keeps it from gelling until it gets much colder. Even if your fuel is warm enough to let the engine start, if it’s thickened at all, it absolutely will increase wear and tear on the engine, decreasing its life and possibly causing damage if it’s thick enough. It decreases its ability to go through your filter, decreasing filter life and effectiveness.

Finally, if your fuel is already gelled up in the engine and fuel tank/fuel lines, you may need an additive that can dissolve and liquify gelled diesel fuel. This is not something you do or want to do on a regular basis, but it is a great product to have in your vehicle just in case you need it to get the vehicle started so the fuel can warm.

Benefits of treating include the aforementioned: Better power, more consistent running, lower wear and tear on your engine, better fuel efficiency, and increased engine life.

Let us dive into each problem and how to stop it with an additive solution!

Diesel Injector cleaners

As you run fuel through your vehicle and it burns in the combustion chamber, if it combusts incompletely, it can leave behind carbon deposits. Carbon deposits are the “gunk” you see in all the pictures in marketing. I have included an example of such a photo here.

AMSOIL Diesel Injector Clean.
AMSOIL Diesel Injector Clean

This problem can be greatly reduced by the use of high-quality fuels, cetane additive, and by ensuring that the fuel is warm or that you have anti gelling agents in it during cold weather. That said, it still happens. You can have the injectors serviced and manually cleaned, and may very well need to do so at some point in the life of the vehicle, but that time can be extended if you use the proper additives for your diesel fuel.

As the injector gunks up, the stream of fuel coming through it is diminished and shaped incorrectly. Modern internal combustion engines, including diesel engines, are machined to incredible tolerances – often down to far less than the width of a human hair. If those get clogged even a little, it can make a material difference in how well the injector delivers fuel to the combustion chamber and thus the power output of the engine.

If left untreated, these formations of crap can completely clog the injector ports. This can lead to misfires, hard starts even when the engine is warm, and very poor performance. At this point, the injector can become so clogged that it cannot be cleaned even with professional servicing and must be replaced with either a new or refurbished injector. This is not only an efficiency and power problem, but a safety problem. Your vehicle needs to start and run well consistently in all seasons.

Rather than letting it get that damaged, it is a good idea to keep your injectors clean. This can be done by using a good diesel fuel additive like AMSOIL Diesel Injector Clean. This fuel injector cleaner is good for all diesel engine designs old and new, including high-pressure common rail injectors. Rather than decreasing the lubricity of the fuel like many injector cleaning additives, AMSOIL’s product increases the lubricity of the fuel, as seen below in this graph:

Lubricity improvement.

Let us take a second to discuss lubricity. Lubrication is critical to the longevity of any engine. If you maximize lubricity in your fuel, you make it a lubricant that leads to reduction in metal-on-metal contact and extend the life and reliability of your motor for miles. A fuel that can keep engine internals lubricated is ideal. Ever since the sulfur content of diesel fuel was reduced due to environmental concerns, lubricity has been a concern.

Updated fuels contain additives straight from the manufacturer, but a diesel fuel supplement specific to lubricity helps ensure ideal characteristics while ensuring a clean burn in the engine.

This not only improves the performance of the engine by cleaning the injectors, it helps ensure the fuel lubricates the engine better and starts more easily. It does not just clean the injection system – it will also help reduce deposits throughout, acting as a fuel system cleaner and corrosion inhibitor.

AMSOIL Diesel Injector Clean also helps separate diesel fuel and water. Low quality fuel can have a high-water content. Cheaper separator fuel supplements use alcohol to separate water, which can destroy some fuel system components.

Diesel Cetane booster

Problem – What Happens?

AMSOIL Cetane Boost.
AMSOIL Cetane Boost

Cetane content is what determines a diesel fuel’s ability to ignite only when it should. Diesel fuels with low cetane take too long to ignite, leading to mis-timed ignition and poor combustion. Over a prolonged period, cheaply fueled engines have more carbon build up, less power, and more emissions. Increasing cetane content decreases gunk in the engine, increases power, and decreases emissions.

Gone are the days of diesels being known for belching black smoke – except for those few folks that do it intentionally! With rising concerns about environmental cleanliness, certain states and local jurisdictions have high requirements for cetane fuel minimums, such as California or certain counties in Texas.

Some gas station chains also offer premium diesel fuels with high cetane content, although the marketing for this is unclear and you really must do your research to know what you are buying – and formulations often change.

An easy way to get this boost and ensure that your fuel is optimized for ignition is to use a cetane booster. A good choice is AMSOIL’s Diesel Cetane boost. This diesel fuel additive can raise the cetane count in your fuel by 4 to 8 points depending on the concentration used. Since the minimum required cetane count is 40, and most common diesel fuels average 44-45, this ensures a minimum of 48 and an average of 52-53. This puts it in the range of the highest quality fuels (Texas high cetane counties require 48 minimums, and California requires 53 minimum), ensuring maximum power and minimum gunking of internal engine components.

While the power boost may not be big over time, it is noticeable for heavy hauling or acceleration. It also has a small but noticeable effect on fuel consumption – your fuel goes further, and you will notice an increase in fuel economy as a result. Furthermore, it prevents longer term power loss through buildup of incomplete combustion deposits inside the engine, meaning the more and longer you use it, the more benefit you will see.

Diesel Cold Flow

AMSOIL Diesel Cold Flow.
AMSOIL Diesel Cold Flow

Diesel fuel can gel anywhere from -18 to 40 degrees Fahrenheit. At some point in this range, dependent on fuel and engine combination, it will get so gelled that the engine cannot start. Long before the fuel solidifies to this point, it will thicken. Cold starting a diesel engine with thickened fuel places immense strain on it and decreases engine life over time.

There are a few ways around this problem, as mentioned previously – you can get a fuel warmer, keep the vehicle in a warm building year-round, or use an anti-gelling additive. The easiest to use and most pragmatic in terms of vehicle storage and parking it at a worksite, parking lot, or anywhere else it will be exposed to extreme cold for more than a few hours is to use a fuel additive.

A good choice for a cold weather improver additive is AMSOIL’s Diesel Cold Flow. This product has several properties that help keep fuel flow reliable. This will prevent gelling by acting as an antifreeze, dropping the gelling point of the fuel by up to 40 degrees Fahrenheit – enough to make a huge difference even in bitterly cold winters.

If you live far enough north that the fuel could still gel, it will also make a fuel heating system much more effective and/or make any heated environment require far less thermal energy and cost to heat enough to keep the fuel thin enough to use. It also does one other thing many other anti-gelling agents do not.

It has an anti-settling agent for the paraffin wax components in diesel fuel. As fuel cools and gels, the wax components settle out, thicken, slow, and stick to each other. This is what makes fuel solidify.

If diesel fuel sits for a long time, this is one of the major reasons it will “go bad.” The wax forms large particles that are heavy enough to settle down to the bottom and stick. AMSOIL’s anti-settling agent decreases the ability of the wax to stick to itself, maintaining tiny particles that rise easily in the fuel. This increases stability and decreases settling, improving fuel life and performance at low temperatures.

This has one other major positive effect: It helps prevent wax buildup in the filter. Cold, thick, waxy fuel can stick to diesel filters and start a clogging process that continues to build over time without freeing. AMSOIL’s additive helps ensure this process never starts, partly curing cold diesel fuel issues. You can see how drastically improved the safe working temperature of diesel fuel becomes with the additive in this chart:

Cold flow improver.

Diesel Recovery

AMSOIL Diesel Recovery.
AMSOIL Diesel Recovery

Sometimes the inevitable happens. You forget to treat your fuel, or get winter diesel, or your winter diesel gels up on you because you had to use diesel fuel from a lower quality source and it just isn’t rated for the cold temperatures you’re facing. There are a few recovery options, most of them unpleasant, expensive, or both unpleasant and expensive.

But AMSOIL has a product that can reduce or eliminate that unpleasantry. It is a very aggressive thawing agent for frozen diesel fuels. It pointedly and specifically attacks wax buildup in the fuel filter itself as well as the rest of the fuel system.

It’s called AMSOIL Diesel Recovery. One of its key features is that it is a dedicated product for emergency use only – meaning you do not use it as a regular additive for your vehicle. Used at a ratio of 1 oz additive to 1 gallon of fuel, it can melt wax and liquify fuel enough to get a diesel engine started up right in the freezing conditions that made it too cool to work.

Unlike other additives, you do not add it to your fuel tank first. Instead, you remove your fuel filter, fill it with Diesel Recovery, reinstall it, and pour the remaining additive to your fuel tank. You will be able to start the engine and let it idle until the product can cycle completely through the fuel system.

AMSOIL’s product has no alcohol (often found in these types of products), which leads to early degradation of fuel system components in some vehicles. It is also non-corrosive and has no chemicals that interfere with or harm fuel system components. It will not damage your fuel system and will not lead to clogging of your fuel filters.

You can consider it a cheap insurance option. If you have to operate diesel vehicles or equipment in extremely cold conditions, it’s a good idea to have a bottle of AMSOIL’s Diesel Recovery and a brand-new fuel filter for every engine critical to your journey or job. If they gum up, you can take a new filter, fill it with Diesel Recovery (a funnel may come in handy and should be part of your emergency preparedness kit along with the treatments for your fuel), and replace the currently gelled filter in the engine. This will lead to a faster, more thorough start up even in the most brutally cold conditions.

Diesel All-In-One

AMSOIL Diesel All-In-One.
AMSOIL Diesel All-In-One

Wow – that is a lot of additives. Four, specifically. Three regular additives for regular use and one for emergency use only. Wouldn’t it be great if we could simplify this for the common man? As a homeowner and homesteader I have to keep track of the chemicals vital to my homesteading success: pesticides, paints, solvents, adhesives, fertilizers, feed, medications for pets and livestock, aquarium and hydroponics additives and nutrients, and any other related products. I do not want to keep track of three things where I can keep track of one.

Thankfully, AMSOIL understands folks like you and me – their three non-emergency, regular use additives come in a combination treatment diesel conditioner called AMSOIL Diesel All-In-One. It combines the characteristics of their Injector cleaner, Cetane booster, and Cold Flow and is one of the best diesel fuel system cleaner and stabilizer products, combining the lubricating, protective, and other characteristics that prolongs engine life.

The AMSOIL All-In-One fuel improver product costs only around $1.20 more per 8oz (less if you compare bulk sizes), and at $6.50 to treat 20 gallons of diesel fuel, it’s a concentrated, low-cost, high-value way to take good care of your engine’s fuel. It meets or exceeds all specifications for diesel fuel additives, and treats summer and winter diesel fuel, biodiesel, and diesel mixes.

Users only need to remember to use and how to use one diesel fuel product as both an extreme clean and boost agent, conditioner, and a fuel stabilizer, and only need to keep one product on hand. All-In-One enhanced fuel parallels the best commercially available diesel fuels in the United States for performance and extending engine health.

Product Recommendations

Here is a quick list of links to the products I have recommended:

Table of Amsoil Products/Links/Bulleted Summary of Benefits

Product Name Intended Use Benefits
AMSOIL Diesel Injector Clean Regular use
  • Cleans fuel injectors in all diesel engines
  • Can be added to any kind of diesel fuel
AMSOIL Diesel Cetane boost Regular use
  • Boosts engine power
  • Decreases crud buildup in engine
AMSOIL Diesel Cold Flow Regular use
  • Allows diesel fuel to flow even in very cold temperatures
  • Decreases wax buildup in filter
AMSOIL Diesel Recovery Emergency use
  • Breaks up wax and frees up gummed and thickened fuel in engines in cold weather
AMSOIL Diesel All-In-One Regular Use

Tips and Tricks

All AMSOIL diesel boosters work for all diesel fuels, including blends and biodiesel. They do not contain ethanol or other alcohols, can be used in varying roles, including farming equipment, by the individual driver or in large fleets, generators, or boats (including heavy tugboats and workboats), effectively meeting any demand for anyone interested in protecting their investment in a diesel engine.

Discussion: Biocide

Diesel fuel can (oddly enough) support certain unique microbes. Unless you have had experience, it might seem unusual that microbes cause a percentage of problems with modern technology like diesel engines, or that protection from microbes is a part of ensuring that filters and pumps are able to function.

While a variety of bacteria and other microbes can lead to buildup of sludge in fuel systems (lines, tanks, etc.), the real trouble starts when the sludge is pumped into the filter. It backs up, plugging the filter, and prevents adequate fuel mobility through the system.

Ideally, you should not let this happen. To prevent fuel microbe growth, you need to use an additive that enhances water removal from the fuel. Microbes in diesel fuel require water to grow, and an additive that eliminates water eliminates the opportunity for their growth. If diesel fuel is the only fluid present, they will have a hard time propagating to the point they are a problem.

AMSOIL’s additives are the types of fuel additives you would want to select. Their All-In-One diesel fuel treatment helps dry fuel from water, preventing fuel from having microbial growth even if it is stored. It is part of how AMSOIL additives act as long-term fuel stabilizers.

If you let fuel sit for a long time untreated and the water and fuel experience separation, you may not notice until you use the fuel in your vehicle and it clogs up your filter, preventing it from allowing good fuel flow and reducing its ability to filter particulates. In recommending an additive I would mention a few biocides – BIOBOR and Diesel kleen are two with good reputations. After using them per the directions, you will want to make sure you use AMSOIL All-in-One to keep your fuel clean.

Without getting too technical, biocides can kill microbes but not necessarily eliminate the carnage they leave behind. You will also need to ensure adequate fuel filtration for your fuel system. It can take a few filters to clear all the waste. Once your fuel reaches workable levels and starts flowing smoothly, you can replace the filter one final time and get back on the road.


You have invested in your diesel engines, whether they are on your car, truck, or equipment. There is no sense in not feeding them a fuel that will keep them running strong for a long, long time. AMSOIL is an old, all-American brand from an old, all-American company. They are trusted and have earned a strong reputation for a reason – they were started by a man that helped found America’s jet fighter program and are still run by the same family.

Their products outclass competition almost completely across the board. I would not recommend them if I did not use them, trust them, and understand and grasp and appreciate the rigorous scientific testing they undergo. AMSOIL has even invented tests for fuel additives that are now considered industry standards. Best part? They do not spend millions on hype or marketing. They rely on guys like me to spread the word and sell their products only through distributors that use, believe in, and truly understand the benefits of their products. As a result, they are not expensive for the quality received.

I can treat a truck tank full of diesel fuel for my family Excursion for $8 of their All-In-One and carry the optimum solution for a cold start problem for $50 (new filter AND the Diesel Recovery product). I hope you try their products, and I look forward to meeting more Americans having an easier time with their diesel engine maintenance!

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